Evidence for a dynamic-dominance hypothesis of handedness

Abstract

Handedness is a prominent behavioral phenomenon that emerges from asymmetrical neural organization of human motor systems. However, the aspects of motor performance that correspond to handedness remain largely undetermined. A recent study examining interlimb differences in coordination of reaching demonstrated dominant arm advantages in controlling limb segment inertial dynamics (Sainburg and Kalakanis 2000). Based on these findings, I now propose the dynamic-dominance hypothesis, which states that the essential factor that distinguishes dominant from nondominant arm performance is the facility governing the control of limb dynamics. The purpose of this study is to test two predictions of this hypothesis: 1) adaptation to novel intersegmental dynamics, requiring the development of new dynamic transforms, should be more effective for the dominant arm; 2) there should be no difference in adapting to visuomotor rotations performed with the dominant as compared with the nondominant arm. The latter prediction is based on the idea that visual information about target position is translated into an internal reference frame prior to transformation of the movement plan into dynamic properties, which reflect the forces required to produce movement. To test these predictions, dominant arm adaptation is compared to nondominant arm adaptation during exposure to novel inertial loads and to novel visuomotor rotations. The results indicate substantial interlimb differences in adaptation to novel inertial dynamics, but equivalent adaptation to novel visuomotor rotations. Inverse dynamic analysis revealed better coordination of dominant arm muscle torques across both shoulder and elbow joints, as compared with nondominant arm muscle torques. As a result, dominant arm movements were produced with a fraction of the mean squared muscle torque computed for nondominant arm movements made at similar speeds. These results support the dynamic-dominance hypothesis, indicating that interlimb asymmetries in control arise downstream to visuomotor transformations, when dynamic variables that correspond to the forces required for motion are specified.

The Effect of Different Movement Exercises on Cognitive and Motor Abilities

“…Previous studies indicated that the dominant arm shows a benefit in controlling the initial movement direction while the non-dominant arm is more proficient in controlling the final posture (Sainburg, 2002;Sainburg & Kalakanis, 2000). Relating these results to the results of our study, it may be accepted that basically the dominant aspect of movement control of the respective arm can be affected by the intervention.…”

Finger force perception during ipsilateral and contralateral force matching tasks

“…On the other hand, the tendency of the dominant hand to overestimate finger forces of the non-dominant hand may indicate that the CNS simply favors the use of a command efferent signal in bimanual tasks. Thus, our findings support the dynamic dominance model of handedness (Sainburg 2002). …”

The extent of interlimb transfer following adaptation to a novel visuomotor condition does not depend on awareness of the condition

“…That is, directional information of the reaching movement only transferred from the left to the right arm, whereas positional information only transferred from the right to the left arm (i.e., the right and the left arms benefited from initial training with the opposite arm only in terms of initial direction and final accuracy control, respectively). They also demonstrated later (Wang and Sainburg 2006) that the two types of information transfer in opposite directions in left-handers, thus supporting the idea that the dominant and nondominant, as opposed to the left and right, limb/hemisphere systems are specialized in controlling dynamic features of movement and final limb posture, respectively (Sainburg 2002). With regard to interlimb transfer of dynamic adaptation, a number of studies have investigated the pattern of dynamic transfer and demonstrated that the pattern of interlimb transfer following dynamic adaptation is somewhat different from that following visuomotor adaptation: directional information transfers only from the right to the left arm of right-handers, and not vice versa (Criscimagna-Hemminger et al 2003;Galea et al 2007;Wang and Sainburg 2004).…”